Age and Growth of Southwestern Atlantic Wreckfish Polyprion

Fisheries Research 66 (2004) 157–169

Age and growth of southwestern Atlantic wreckﬁsh Polyprion americanus Monicaˆ Brick Peres a,∗, Manuel Haimovici b a Região do Litoral—Departamento de Qualidade Ambiental, Fundação Estadual de Proteção Ambiental—FEPAM, Carlos Chagas 55, Porto Alegre RS 90030-020, Brazil b Fundação Universidade Federal do Rio Grande—FURG, Cx. Postal 474, Rio Grande RS 96201-900 Brazil Received 6 February 2002; received in revised form 23 May 2003; accepted 10 July 2003

Abstract Southwestern Atlantic wreckfish Polyprion americanus (27◦56S and 34◦52S) were aged using transverse thin sections of the sagittae otoliths of 390 individuals (44–155 cm TL, total length). The index of average percentage error for independent readings of two readers was 3%, and 10% of the sections were considered illegible. Marginal state assessment of the whole otolith’s margin (n = 406) showed that one opaque band (annulus) is laid down each spring–summer. Supposed daily ring counts confirmed what was thought to be the first annual band. Maximum observed age was 76 years for males and 62 years for females. The von Bertalanffy growth model was significantly different (P<0.01) between males (L∞ = 109.5cm, K = 0.084 per year and t0 =−4.69 years) and females (L = 129.5cm,K = 0.0534 per year and t0 =−6.80 years). The absence of wreckfish below 44 cm TL in the samples and younger than 1.5 years means that this is the minimum size and age of recruitment to the bottom. © 2003 Elsevier B.V. All rights reserved.

Keywords: Age; Growth; Whole and sectioned otolith; Wreckﬁsh; Polyprion americanus

1. Introduction allelic variation at microsatellite loci differentiated wreckfish from two southern hemisphere locations, Wreckfish, Polyprion americanus (Bloch and Schn- Brazil and the south Pacific (Ball et al., 2000). eider, 1801), of the family Polyprionidae (Eschmeyer, Along southwestern Atlantic P. americanus occurs ◦ ◦ 1990), is a large demersal fish that inhabits continen- from 23 S, near Rio de Janeiro, Brazil, to 46 S, Ar- tal and oceanic islands slopes of temperate and sub- gentina (Cousseau and Perrota, 1998; Peres, 2000). A tropical waters at both sides of the Atlantic Ocean, at wreckfish fishery with handlines from small boats off the Mid-Atlantic Ridge, the Mediterranean, southern southern Brazil is recorded since 1973 (Santos and Indian Ocean and southern Pacific (Heemstra, 1986; Rahn, 1978; Barcellos et al., 1991). In the nineties, the Roberts, 1989, 1996; Sedberry et al., 1999). Recent fishery changed to vertical longlines and then to steel studies using mtDNA and microsatellite, differen- wire longlines. The number of vessels increased from tiated northern and southern wreckfish stocks, and around 10 in the 1970s, to more than 35 in 1997. Al- though fishing power grew with gear development and ∗ Corresponding author. Tel.: +55-5132132124227; expansion of fishing area, estimated annual landings fax: +55-5132251588. decreased from 2772 (1989) to 1080 t (1995). Cap- E-mail address: [email protected] (M.B. Peres). ture (kg) per hook, per days at sea, dropped from 0.72

(1989) to 0.48 (1997–1998). This suggests that this from research surveys with bottom trawl (1986–1987) stock may be endangered and needs to be managed and longline (1996–1997) (Table 1). The study area (Peres, 2000). was the continental shelf and slope off southern Brazil Age estimates from band counts on aging structures (27◦56S and 34◦52S), in water depths from 70 to and validation of the periodicity of their deposition are 500 m. basic requirements to obtain growth rates, ages at ma- In research cruise samples, fish total weight (TW in turity and recruitment, longevity and natural mortality kg) and total length (TL in cm) were recorded. Length rates. These are essential data for proper management was measured between the end of the inferior jawbone of southwestern Atlantic wreckfish. and the end of the tail in natural position. Sex was Band patterns on otoliths sections of Polyprion determined by external examination of the gonads and species have been considered unreliable (Paul, 1992) both otoliths were stored dry for aging. or difficult to count (Francis et al., 1999). P. oxy- Wreckfishes from commercial landings are sold ice geneios (New Zealand hapuku) may attain more than cooled and ungutted. As each fish may attain large 60 years of age (Francis et al., 1999) and P. ameri- body size and high prices, sampling procedures re- canus (southeastern USA wreckfish) up to 39 years quired fast and non-damaging techniques. Fish were (Vaughan et al., 2000), but there are no age estimates measured from the posterior border of the eye orbit to for P. americanus stocks in the southern hemisphere. the fork of the caudal fin (EF in cm) and converted to Here, the otolith transverse sections were chosen for TL by the relationship TL =−0.724+119.5EF (Peres age determination. The development of a method to and Haimovici, 1998). Sex was determined by extract- prepare and read otoliths sections and find the period- ing a small sample of the gonad with a surgical curette icity of band formation, made it possible to determine through the gonopore and the left otolith was obtained longevity and growth models for male and female through the opercular openings and stored dry. southwestern Atlantic wreckfish P. americanus. 2.2. Readings on the otoliths

2. Material and methods Whole otoliths of 406 wreckﬁsh of both sexes (44–155.5 cm TL), immersed in 70% ethanol for 24 h, 2.1. Sampling were examined with incident light over a black background. Thin transverse sections through the focus Biological samples were obtained from commercial were obtained from otoliths embedded in a polyester landings (1990–1995) with different ﬁshing gears and resin with a single high concentration diamond wheel

Table 1 Sampling period, fishing gear, fishing area, TL (mm) and number (n) of fish examined for age and growth study of southwestern Atlantic wreckfish Period Gear/typea Fishing area TL (cm) n Latitude Water depth (m)

1986/1987 BT/res 31◦50–34◦52S 120–450 57–115.5 43 1990 FT/com 33◦55S 70–90 44–51 22 1994 VL/com 30◦45–34◦04S 250–400 64–150.5 24 1994 BG/com 33◦25–33◦43S 220–320 44–132.5 27 1995 VL/com 28◦40–34◦49S 280–460 62–155.5 83 1995 L/com 30◦05–32◦13S 400–420 54–140.5 114 1995 BG/com 33◦30–33◦50S 90–320 44–130 31 1996/1997 BL/res 27◦56–34◦29S 130–500 49–123 62 Total 27◦56–34◦52S 70–500 44–155.5 406 a BT: bottom trawl; BG: bottom gillnet; BL: bottom longline; FT: ﬁsh traps; VL: vertical line and hook; L: longline; res: research cruise; com: commercial. M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169 159

Fig. 1. Transverse otolith section, 0.18 mm thick, observed with transmitted light (32×). Otolith from a female wreckfish (127 cm TL) captured in October 1995 off southern Brazil. Counted opaque annual bands (white or black circles), sulcus acusticus (SA), internal face (IF), external face (EF), ventral margin (V), focus (F), first opaque band (1), first discontinuity (D), false ring (FR). with a Burhler-Isomet low-speed saw. Band patterns For 3.6% of them, agreement was not possible and the were clearer in sections of 0.20–0.25 mm thick for the other 6.9% were considered unreadable by one or both smaller fish (TL < 75 cm) and 0.15–0.20 mm thick, readers. The index of average percentage error (IAPE, for larger ones. Sections with more than 30–40 bands Beamish and Fournier, 1981), was calculated as were ground further on 1000-grade sandpaper until N R 0.11–0.15 mm thick. All sections were mounted on 1 1 |Xij − Xj| IAPE = glass slides with xylol base mounting media (ENTE- N R Xj j=1 i=1 LAN Merck). Undamaged otolith sections (n = 390) were exam- where N is the number of fish aged, R the number of ined with transmitted light under a compound micro- times each is aged, Xij the ith age determination of the scope (40–100×). Opaque bands were counted from jth fish and Xj the average age calculated for the jth the focus to the outer edge of the sulcus (Fig. 1). Thin- fish. The IAPE between independent counts (n = 2) ner sections (0.11–0.15 mm thick), usually from older was 2.91%. fish, were also examined with incident light under a Narrow opaque bands, assumed to be daily rings dissecting microscope with low magnification to con- (Campana, 1992), were examined on the otoliths firm the band patterns on the central area near the sections of four wreckfish (45–90.5 cm TL, 2–22 focus. After several preliminary readings, final indi- years old). The sections were hand ground until vidual blind counts were made independently by two 0.04–0.09 mm thick and mounted on glass slides with readers. If band counts differed, both readers exam- mounting media. They were counted from the focus ined the section together and if no agreement could be to the first discontinuity (Fig. 1), along the external reached the otolith was rejected. face, on a compound microscopy (400–1000×). This Counts between successive readings of the same discontinuity was similar to the ultra structures in the reader and between the two readers varied due to (1) otoliths of the eel Anguilla anguilla (Lecomte-Finiger, high number of bands, (2) splitting of opaque bands 1992). Differences of maximum and minimum counts in some portions of the section, or (3) very irregularly for three readings of each section by the same reader spaced bands. Initial agreement between independent did not exceed 9.9% (Table 2). readers was 30.5% and disagreement by only one band The terminology used to otolith description was was 26.5%. Following a common reading and discus- adapted from Wilson et al. (1987) and Moralis-Nin sion 89.5% of the otoliths were considered readable. (1992) (Table 3). 160 M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169

Table 2 Number of narrow opaque bands, considered daily, on wreckﬁsh otolith sectionsa TL (cm) Age Sex FC FD(1) FD(2) FD(3) FD(mean) %

49 3 Female 137 373 356 362 363.7 4.78 90.5 22 Male 155 387 372 384 381 4.03 54 3 Male 141 393 382 386 387 2.88 45 2 Unknown – 400 364 368 377.3 9.89 a For each section, length, age and sex of the fish, number of daily bands from the focus to the end of the central opaque area (FC), number of daily bands from the focus to the first discontinuity (FD) for three counts (first, second and third), the mean number of daily bands and the percent difference (%) between the minimum and maximum number counted on each section.

2.3. Validation at age t (years), L∞ the assintotic length (cm), K the growth coefficient (per year) and t0 the theoret- The periodicity of band depositions was assessed by ical age at zero length (years). Growth curves be- monthly proportions of opaque margins in sectioned tween sexes were compared with a likelihood ratio test and whole otoliths. The posterior end of the whole (Kimura, 1980; Cerrato, 1990), for immature (TL < otoliths was chosen for younger fish and the edge of 75 cm), adults (TL > 75 cm) and for all wreckfish the rostrum for older ones (Fig. 2). together. Length–weight regression for sexes combined (n = 2.4. Growth 207, 44–145.5 cm TL, 1.2–53 kg TW, r2 = 0.98) was W = (6.29×10−6)L3.21 (Peres and Haimovici, 1998). Length at age data was fitted with non-linear it- Weight at age was calculated using this relationships erative procedure (Gauss–Newton) to the von Berta- and estimated length at age. lanffy growth model (von Bertalanffy, 1938), VBGM: Ages were assigned based on annuli counts, as- −K(t−t ) Lt = L∞(1 − e 0 ), where Lt is the length (cm) suming 1 September as the theoretical birthday,

Table 3 Terminology used to otolith description of southwestern Atlantic wreckfish, adapted from Wilson et al. (1987) and Moralis-Nin (1992) Annulus (opaque band) A concentric mark on any ageing structure that allows interpretation of growth in terms of age. In whole and sectioned wreckfish otolith, concentric and continuous opaque bands with a discontinuity, white under incident light and dark with transmitted light were counted as annual bands Central area In the wreckfish otolith it is an area between the focus and the first translucent annual band (associated with a depression on the external face). It is predominantly opaque. In whole otolith, it can be large and diffuse, or composed by one to three opaque areas, considered false rings. On the sections, it was the most difficult portion to interpret the growth band pattern Discontinuity This was the main criterion used to identify the first annual band on wreckfish otolith sections. It is a concentric and continuous structure like “thin crack” when viewed under a compound microscope (50–100×) in otolith sections of less than 0.15–0.17 mm thick. It is found, usually, between the end of the translucent band and the beginning of the opaque one Daily ring On wreckfish otolith sections (0.04–0.09 mm thick), narrow concentric and continuous opaque bands, with smooth transition in width and contrast were counted as “daily” bands Area, region, zone, mark Auxiliary terms used to describe the ageing structures, with no relation with a temporary scale False ring Any opaque area similar to an annual band but interrupted or without a “discontinuity” (if in the central area of the section) Focus Real or hypothetical origin of the whole or sectioned otolith, used as a reference to begin counts or measurements of growth bands. On wreckfish otolith the focus is opaque. Under incident light and dark bottom, the focus appears as a small brilliant white circle in the central area of the lateral face (concave). In the sections, under transmitted light, it is a dark circular area in the central area, near to the margin of the lateral face M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169 161

Fig. 2. View of the left otolith from a female wreckfish, 145.5 cm TL and 51 years old, captured in November 1994 off southern Brazil. Otolith external face observed with reflected light over a dark background. Ventral margin (V), dorsal (D), posterior (P), anterior (A), first translucent band (first TB), first opaque band (first OB), antero-posterior axis (APA), original antero-posterior axis (APO). Magnified opaque otolith rostrum’s edge (10×). Otolith dorsal view showing the otolith curvature, external face (EF), and internal face (IF). considering the spawning season in the region (Peres, 3.2. Band patterns on sectioned and whole otoliths 2000). Viewed with transmitted light, otolith sections have a dark central area (opaque) around the focus and a 3. Results dark line that radiates along the external face surface (Figs. 1 and 3a). Translucent bands were wider than the 3.1. Otolith structure opaque ones near the focus but this width difference progressively diminished from the focus to the border. In wreckfish, the sagittae otoliths are elongated, lat- For the same otolith, width of the translucent bands erally compressed, curved and very fragile (Fig. 2). increased with thinner sections. Their surfaces are irregular, with many mounts and On the sections thinner than 0.15 mm, it was pos- crenellations. The external face of the otolith is con- sible to observe a structure like a “thin crack”, the cave with grooves and ridges radially disposed. With discontinuity, between the end of the first translu- age, the rostrum becomes conspicuous and curved, the cent band and the beginning of the first opaque sulcus acusticus gets deeper and the irregularities on band. Thin transverse otolith sections (0.04–0.09 mm) the surface get strongly marked. The antero-posterior showed pairs of opaque and translucent narrow bands axis rotates during otolith growth and for older fish it (Fig. 3b). The mean number of these bands, consid- may be up to 30◦ or 40◦. Due to this rotation, trans- ered daily rings, from the focus to the first disconti- verse sections through the focus changed planes with nuity was 377.3, almost 1 year (Table 2). Thus, for ages. wreckfish, the discontinuity and the end of the first 162 M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169

Fig. 3. Transverse otolith section (0.04 mm thick) of a 54 cm TL wreckfish, captured in September 1994 off southern Brazil. (a) Observed with transmitted light (32×). Annual opaque bands (black circles), sulcus acusticus (SA), internal face (IF), external face (EF), first translucent band (first TB), focus (F). (b) Observed in higher magnification (1000×) showing general aspect of the narrow opaque bands, considered daily rings, in the opaque otolith central area, adjacent to the external face near to the first annual translucent band. crest on the external surface of the otolith were both same otolith had different classifications. This was due used as criteria to detect the first annual band. One to either extremely thin opaque bands at the border or to three translucent narrow translucent rings were misinterpretation of the border type caused by optical frequently observed before the first annual band, and distortions. were considered false (Fig. 3a). Examined with incident light over a black back- The following continuous opaque bands were con- ground, the central area of whole otoliths is brilliant sidered annual and counted on the dorsal margin of white and may show one to three false rings. The first the sulcus (Fig. 1). Some were very irregularly spaced translucent band is always associated with a depres- and this was considered the main cause of low precision. The central area is surrounded by a clear and sion of preliminary readings. Although they were fre- distinct opaque band, the first annual band (Fig. 2). quent, for each section their number was never more The following 6–12 bands could be easily observed in than 1–5. Counting every band, independent of their the posterior and dorsal region of the otoliths and the spacing resulted in lower IAPE. others along the rostrum. The border type, opaque or The border type was inconsistently classified be- translucent, was consistently classified between two tween successive readings for 62.2% of the 390 otolith independent readings of the same reader for 80.3% of sections. Sometimes, even sequential sections of the the 406 otoliths. M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169 163

30 Whole otoliths 20

0 0 10 20 30 40 50 60 70 80 Sectioned otoliths

Fig. 4. Number of opaque bands counted on whole and sectioned otoliths of southwestern Atlantic wreckﬁsh. It also shows the bisection line.

Age determinations were similar for sectioned and 3.3. Validation whole otoliths, although the number of opaque bands on otolith sections was progressively higher for older Periodicity of band depositions was validated by ﬁshes (Fig. 4). This indicates that the best age esti- monthly proportions of opaque margins of whole mates are on sectioned otoliths. Co-linearity between otoliths (Fig. 5, Table 4). For adult wreckﬁsh (n = readings on whole and sectioned otoliths means that 290, 75–155.5 cm TL) almost 100% of the legible the band patterns are the same and the used criteria borders were opaque from November to February and for band counts are consistent. less than 5% from April to June. Despite the smaller

1.0

0.8

0.6

0.4

0.2 T O 0.0 JFMAMJJASOND I Months

Fig. 5. Monthly proportion of border type, translucent (T), opaque (O) and illegible (I) observed in whole otoliths (n = 406) of southwestern Atlantic wreckﬁsh. 164 M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169

Table 4 Number of opaque margins (O), translucent (T) and illegible (I) observed per month, on whole wreckﬁsh otolithsa Month Immature Adults A Adults B % n

TOITOITOIT O I

January ––––53 –143– 76.0 24.0 25 February – 1–––– ––– – 100.0 – 1 March 14 46832 42554.2 18.8 27.1 48 April 16 2 – 23 – 10 3 – 1 76.4 3.6 20.0 55 May – – 1 14 – 2 12 1 – 86.7 3.3 10.0 30 June 1 ––4–– 1–185.7 – 14.3 7 July 17 1 3 31 14 8 29 2 4 70.6 15.6 13.8 109 August 4 321–– 31444.4 22.2 33.3 18 September 5 12 2674 43730.0 44.0 26.0 50 October – 4–173 29210.7 71.4 17.9 28 November – 6–––– –42 – 83.3 16.7 12 December – 10 2–11 –72 – 78.3 21.7 23 Total 57 43 16 88 37 33 58 43 31 19.7 406 a Immature wreckfish (TL < 75 cm), adults A (75 cm < TL < 100 cm) and adults B (TL > 100 cm). Percentage of translucent, opaque and illegible margins within total number of examined otoliths per month (n). sample size, the same pattern was observed for im- 3.4. Growth mature fish (45–75 cm TL, n = 116). It is concluded that, annually, one opaque band is laid down from As growth differences were not observed between late winter to summer. Higher proportions of illeg- sexes for immature fish (Table 5), 22 unsexed wreck- ible margins (non-coincident or doubtful) occurred fish (44–55 cm TL, 1–3 years old) were included in the during transitional months, when fishes are beginning VBGM for males, females and gathered sexes. Growth to deposit opaque (August–September) or translucent was significantly different between sexes, of adults (March) material on the otoliths (Fig. 5, Table 4). and of all wreckfish together (Table 5). So, growth

Table 5 Maximum likelihood comparison for the VBGM parameters between sexes of southwestern Atlantic wreckﬁsha

H0 Equal L Equal K Equal t0 All equal Immature (TL < 75 cm) (n = 53) Observed F 0.4182 0.2131 0.2359 0.4461 Fixed F (0.05) 4.05 4.05 4.05 2.8 Probability 0.4932 0.6243 0.6064 0.685 Accepted Accepted Accepted Accepted Adults (TL > 75 cm) (n = 265) Observed F 9.33 4.43 2.02 22.12 Fixed F (0.05) 3.88 3.88 3.88 2.64 Probability 0.0022 0.03409 0.1509 <0.00001 Rejected Rejected Accepted Rejected All (n = 328) Observed F 131.88 9.04 2.44 22.25 Fixed F (0.05) 3.87 3.87 3.87 2.63 Probability <0.00001 0.0026 0.1156 <0.00001 Rejected Rejected Accepted Rejected a The curves were adjusted and compared for immature ﬁsh (TL < 75 cm), adult (TL > 75 cm) and all together. The observed F,ﬁxed F (P = 0.05), the probability that the null hypothesis (H0) is accepted or rejected. M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169 165

60 30 0

140 120 100 80 60 40

Total length (cm) 20 0 (a) -100 10203040506070800 55 110 Age (years)

40 20 0

160 140 120 100 80 60 40 Total length (cm) 20 0 (b) -100 10203040506070800 65 130 Age (years)

Fig. 6. Age at length data and fitted VBGM for southwestern Atlantic wreckfish. Frequency distributions of ages and lengths are shown at respective axes. (a) Males (n = 141) and unsexed fish smaller than 55 cm TL (n = 22). (b) Females (n = 174) and unsexed smaller than 55 cm TL (n = 22). See text for parameter values.

−0.063(t+6.30) rates between sexes become different after sexual mat- Ltboth sexes = 121(1 − e ) uration. Females attain larger sizes than males of the (n=337, S.E.=9.207,r2 = 0.85) same ages (Fig. 6). Ages varied from 1 to 76 years old for males (n = 141, 47–126 cm TL), 1–62 years for Growth equations in weight were females (n = 174, 45.5–155.5 cm TL) and the ﬁtted − . (t+ . ) . Wt = 21.8(1 − e 0 084 4 69 )3 21 VBGM were males −0.053(t+6.80) 3.21 Wtfemales = 37.5(1 − e ) −0.084(t+4.69) Ltmales = 109.5(1 − e ) (n = 163, S.E. = 6.886,r2 = 0.90) 4. Discussion = . ( − −0.053(t+6.80)) Ltfemales 129 5 1 e The difﬁculties to get consistent reading criteria (n = 196, S.E. = 9.129,r2 = 0.88) leading to low counting precision were described for 166 M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169

New Zealand hapuku, P. oxygeneios (Francis et al., number of these bands from the focus to the end of 1999). USA wreckfish, P. americanus have been con- the otolith central area (the opaque portion before the sidered one of the most difficult fish species to age assumed first annual band) was 144. This is about the (Potts, 2000). Aging southwestern Atlantic wreck- number of days of the opaque deposition period ob- fish, P. americanus, was possible by counting the served for older wreckfish. The mean number of nar- opaque bands (annulus) in transverse sections of the row bands, from the focus to the first annual opaque sagittae otoliths. It was shown that one opaque band band (discontinuity) was 377, almost the number of is deposited each spring–summer. The number of days in 1-year period. These results together indicate bands increased with body size and spacing between that (1) the narrow bands might be considered daily them decreased gradually from the focus to the mar- marks; (2) the criteria used to identify the first annual gins, confirming their adequacy for age and growth band are adequate; (3) the deposition of opaque mate- studies (Brennan and Cailliet, 1989; Casselman, rial during the first year follows the observed pattern 1990). for older fish. Even with circumstantial evidence that Here, when wreckfish otoliths were sectioned at the narrow bands are daily growth marks, we empha- usual thickness (0.3–0.5 mm), band patterns were sized the need for a further validation of wreckfish unreliable. The lack of sharpness of the growth daily rings. bands observed in several age and growth studies of The difficulty to assess marginal state in otolith Polyprion species is probably caused by the irreg- sections was also observed for New Zealand hapuku ularities on the otolith surface. Narrow deposition (Francis et al., 1999). The monthly proportion of layers on these irregular surfaces and sectioned in opaque margins in whole otoliths permitted us to different planes (in part, caused by the torsion of the validate the periodicity of band deposition on south- antero-posterior axis) may produce “ghosts” of adja- western Atlantic wreckfish otoliths. Except for very cent bands, making it difficult to delineate the limits young fish, the clearer margin pattern was at the edge of each band, and therefore, count them. This is why of the otolith rostrum, presumably because it has a thinner sections (0.11–0.15 mm) resulted in clearer high rate of deposition (the fastest growth axis) and band patterns, specially for older fish where annual its surface is more regular than the rest of the otolith. bands are narrower spaced and the irregularities on This method might be applied to other species with the otolith surface are strongly marked. irregular otolith surfaces and unreliable margins on Besides thinner sections, aging was much improved otolith sections, such as the Serranidae species, to by clear definition of the criteria used to identify the which Polyprion has traditionally been aligned. first annual band, because the otolith central area Processes controlling otolith growth are still not may show one to three false rings. These criteria completely explained. Some authors believe that included the observation of growth features on the opaque or translucent band formation is linked with surface of whole and sectioned otolith (the ridge, external factors as water temperature, photo period associated with the central area, and the groove, asso- or food availability. Others, associate the type of ciated with the first translucent annual band) and the band deposition with endogenous events as repro- presence of a “discontinuity”. Ridges on the otolith duction, migration or physiological stress. Fishes surface have been used as an auxiliary criterion to inhabiting temperate waters usually deposit fast define annual rings of Seriola dumerili (Thompson growing—opaque bands—in summer months and et al., 1999) and Istiophorus platypterus (Prince et al., slow growing–translucent bands—in winter (Pannela, 1986). 1980; Chilton and Beamish, 1982). Secor and Dean Daily rings of other fish species (Stevenson and (1989) observed that when otolith growth is fast, the Campana, 1992) are very similar to the narrow opaque deposition is opaque, lightweight and contains more bands counted on wreckfish otolith microstructure protein. During slower growing period, the deposition (400–1000×). Wreckfish spawning season in the is translucent, heavier than the opaque one and has study area is from late July to early October (Peres, less protein and more calcium. Wright (1991) showed 2000) and coincides with the beginning of the depo- that the otolith growth of Salmo salar is related to a sition of the opaque material on the otolith. The mean high metabolic rate and not to fish body growth. M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169 167

For New Zealand hapuku, austral winter–spring is tremely difficult (Roberts, 1996; Sedberry et al., 1996; the time of opaque band formation (Francis et al., Francis et al., 1999). Francis et al. (1999) estimated 1999), about the same period observed for south- for New Zealand hapuku a pelagic phase of 3–4 years western Atlantic wreckfish, late winter to summer. (about 50 cm TL). From a sample of 7654 southwest- In the study area (1) water temperatures in the sum- ern Atlantic wreckfish, caught with different gears, no mer (below 80 m) are 3 ◦C higher than in winter fish were smaller than 44 cm TL, only 5 were below (18.5–15.5 ◦C) (Bakun and Parrish, 1991); (2) due 45 cm TL (0.07%) and 50 fishes were 45–50 cm TL to slope upwellings in winter–spring (Garcia, 1997), (0.7%) (Peres, 2000). All sampled fish below 55 cm ocean productivity and food availability are higher TL were aged. Wreckfish from 44 to 45 cm TL were (Ciotti et al., 1995); (3) in winter–spring, adult wreck- 1.5–2.5 years old, so this is the size and age of the fish does a northern migration to spawn and has a recruitment to the bottom in the study area. higher food uptake (Peres, 2000). These events may Negative values of t0 are frequent among species all be related to higher metabolic rates of southwest- with rapid growth during the first year and reduced ern Atlantic wreckfish. growth rates in the following years (Sadovy et al., Body sizes of USA wreckfish captured with line 1992; Newman et al., 1996; Craig et al., 1997). There and hook were 75–146 cm TL (Sedberry et al., 1999). are no data on the 1-year-old wreckfish in the study New Zealand hapuku captured with bottom trawl were area, but the results indicate that their lengths should 41–147 cm TL, but most fish were less than 85 cm be around 35 or 40 cm. The growth rate of southwest- (Francis et al., 1999). The size range of aged southern Atlantic wreckfish in its pelagic phase must be western Atlantic wreckfish (44–155.5 mm TL), cap- faster than the observed after the settlement to the bot- tured with several fishing gears was about the same as tom. Fit two VBGM, one for the pelagic and one for in other studies. Despite having just a few large fish, demersal phase, could be a solution (Vooren, 1977; the maximum observed age for hapuku was 63 years, Craig et al., 1997). However, there are no catches of not far from the maximum ages observed for south- wreckfish juveniles (<1.5 years) off southern Brazil. western Atlantic wreckfish (62 years for females and So, we consider that the fitted VBGM describes 76 years for males). Maximum age for USA wreck- body growth with age, for male and female, for the fish stock was 39 years (Vaughan et al., 2000), about size range recruited to the bottom and commercially half of the other studies. Here, counting all continu- exploited. ous opaque bands, even some which could be false rings (very irregularly spaced), might have generated some overestimated readings. But this cannot explain Acknowledgements the observed differences because the number of these bands was never more than one to five for each otolith This work was originally submitted as part section. of a Ph.D. thesis to the Biological Oceanogra- The K values obtained here (0.053 females, 0.084 phy Pos-Graduation, Universidade de Rio Grande males) were similar to those of hapuku, 0.061–0.079 (FURG)—Brazil, and was supported by grants from gathered sexes (Francis et al., 1999) and USA wreck- Brazilian Ministry of Education (CAPES). Thanks to fish, 0.073 also for sexes together. The t0 values of Antonio Bianchi for access to his wreckfish catches the VBGM obtained for all Polyprion species were and to many fishers during biological sampling. We strongly negative: −6.80 and −4.69 years for south- thank Lucio Waengertner Pires, who developed the western Atlantic wreckfish; −12.48 and −16.56 years technique to extract wreckfish otoliths from commer- for USA wreckfish (Vaughan et al., 2000); −4.06 to cial landings and for field assistance, and to Carolina −5.75 for New Zealand hapuku (Francis et al., 1999). Araújo who photographed otoliths sections. Many This might indicate that VBGM does not fit the data thanks to Carolus Maria Vooren and Sandro Klippel for small fish or may be due to the absence of small for critical reviews and helpful comments on earlier fishes in the samples. versions of the manuscript. Special thanks to Beat- Juveniles of Polyprion species are pelagic, live asso- rice Padovanni Ferreira for advice, reviews of the ciated with floating objects and capturing them is ex- manuscript and much fruitful discussion. 168 M.B. Peres, M. Haimovici / Fisheries Research 66 (2004) 157–169

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